Process for false twist-crimping yarn



y 1967 R. s. GILCHRIST 3,318,083

PROCESS FOR FALSE TWIST-CRIMPING YARN Filed May 8, 1964 United States Patent O 3,318,083 PROCESS FGR FALSE TWlST-CRIMPING YARN Reginald Selby Gilchrist, London, England, assignor to The Klinger Manufacturing Company Limited, London, England Filed May 8, 1964, Ser. No. 366,693 Claims priority, application Great Britain, May 10, 1963, 18,712/63 4 Claims. (Cl. 57--157) This invention relates to a method for false twist crimping yarn formed from organic synthetic material including polyamides, polyesters, and material sold under the trade names nylon and Perlon and under the registered trademark Terylene and which method is carried out using apparatus of the kind comprising two twisting heads arranged to apply false twisting to the yarn first in one direction and then in the opposite direction and means for heating the two stretches of the yarn on their way to the twisting heads respectively. One form of this apparatus is disclosed in British patent specification No. 788,944. The heating conditions to which the yarn is subjected before reaching the two twisting heads may require to be substantially different and to vary for different kinds of yarns and an object of the invention is to provide an apparatus suited for these conditions.

According to this invention a method of producing crimped yarn comprises heating and false twisting the yarn, then subjecting the yarn to a second heating and false twisting, wherein the two false twisting operations twist the yarn in opposite directions, the degree of twisting in the second false twisting operation being not less than in the first twisting operation. The degree of twisting in the second operation may be the same as in the first operation.

The yarn may be heated during the first false twisting operation to a greater extent than during the second false twisting operation, for example, by heating the yarn for a longer time during the said first false twisting operation than during said second false twisting operation. Alternatively a shorter length of yarn may be subjected to heating in the second operation than in the first operation.

The temperature to which the yarn is subjected may increase along the length of the yarn. In such a method the maximum temperature to which the yarn is subjected in the first operation may be greater than in the second operation.

In any of these methods the heating of the yarn during the second false twisting operation may be effected by the same heating maens as used for the first false twisting operation.

Preferably the yarn is under tension when first being heated but is under little or no tension during the second heat treatment.

The stretches of yarn may be drawn from the two twisting heads at the same speed or at dilferent speeds.

The yarn after leaving a supply bobbin preferably moves continuously into the first and second heating and false twisting zones to a take up bobbin.

An apparatus for false twist crimping yarn according to the method of the invention may comprise two twisting heads arranged to apply false twisting to the two stretches of the yarn entering them, first in one direction and then in the other, means for heating the two stretches of the yarn on their way to the two crimping heads respectively and means for varying the length of contact of at least one stretch of the yarn with the heating means.

One form of the apparatus may comprise a heating means, a supply bobbin at one end of the heating means, two twisting heads disposed at the opposite end of the heating means to the bobbin, a pair of guide means at the same end of the heating means as the bobbin, a second pair of guide means at the opposite end of the heating means, yarn traversing mechanism on the opposite side of the twisting heads to the heating means, yarn winding mechanism and a third pair of yarn guides associated with the yarn traversing and winding mechanisms, the arrangement being such that a stretch of yarn is drawn off the bobbin, passes through one of the guides of the first pair and through or over the heating means, through one of the guides of the second pair, through one of the guides of the third pair back again to the other guide of the first pair so that a second stretch of the yarn passes through or over the heating means and through the other guide of the second pair and through the second twisting head and thence to the yarn traversing means and finally through the other guide means of the third pair to the winding mechanism.

The heating means may comprise a single heating surface over which the two stretches of the yarn pass side by side travelling in the same direction.

At least said other guide of the second pair of guide means is adjustable in a direction towards and away from said heating surface.

Tensioning means may be provided between the bobbin and the first said guide of the first pair of guide means.

The invention includes within its scope a crimped yarn produced by the method and apparatus as set out above and also includes a hose knitted from a crimped yarn of 15 to 40 denier.

The following is a description of one form of double false twist crimping apparatus according to the invention reference being made to the accompanying diagrammatic drawing.

The yarn is fed from a supply bobbin 10 through a gate tensioner 11 and around an adjustable magnetically restrained pulley 12 of known form. The yarn passes downwardly from this pulley around a guide 13 beyond the lower end of a bowed heating surface 14. The temperature of this surface increases from the lower to the upper end thereof in the manner described above.

The yarn after passing along a groove formed in this surface leaves the upper end thereof and passes through a guide 15.

The two guides 13 and 15 are so disposed that the yarn is maintained in contact with the bottom of the groove in the bowed surface 14 over the whole length thereof. The yarn passes from the guide 15 up through a first false twisting head 16 and from there passes around a guide 17 and around an upper nip roller 18 which is spring pressed against a centrally disposed driving roller 19. The yarn passes from between the nip roller 18 and driven roller 19 around a guide 2t} and at this stage it has received a false twist in one direction.

The false twisted yarn is fed downwardly by the action of the rollers 18 and 19 around a guide 21 and on to a freely rotating pulley 22.

The yarn passes downwardly from this pulley 22 around another guide 23 disposed below the lower end of the heater 14.

The yarn passes upwardly from this guide 23 into the lower end of the aforesaid groove in the bowed face of the heater and through a guide 24 which is so disposed that the yarn leaves the heated surface at a point 25.

The yarn then passes through a second false twisting head 26 which rotates the yarn in the opposite direction to the first said head 16 and at the same rate and passes thence around a guide 27 and around a lower nip roller 28 which is spring pressed against the driving roller 19. It passes from between these rollers around the aforesaid guide 27. The yarn has then been subjected to false twisting in two opposite directions successively resulting in a crimped yarn in which the torsional strains are substantally balanced.

The double false twisted yarn then passes around a guide 29 on to a wind-up bobbin 30 which is rotated in conventional manner by a friction roller 31.

By the preferred embodiment of the invention it is possible to obtain a more bulky substantially non-torque crimped yarn.

This bulky substantially non-torque crimped yarn is particularly useful for fine deniers, for example to 40 deniers, used for the manufacture of fine gauge hose such as, for example womens stockings.

The crimped yarn is particularly useful in the manufacture of womens stockings made by 51 to 66 gauge fully fashioned stocking knitting machines and 370 to 500 needle circular stocking knitting machines, these circular stocking knitting machines preferably having a diameter of 3 /2 to 4 /2 inches.

The second false twisting operation preferably slightly overrides the effect of the first false twisting operation so that the yarn immediately after double crimping has a slight residual torque in the direction imparted to it by the second false twisting operation; however, after wetting, for example during dyeing or wet relaxing of fabric knitted from the crimped yarn, this slight overriding of the second false twisting operation disappears.

To obtain the bulky substantially non-torque crimped yarn that is particularly suitable for fine gauge hose, it is necessary for the degree of twist imparted to the yarn by the second false twisting operation to be equal to or greater than that imparted to the yarn by the first false twisting operation.

A further feature in the production of this particular yarn is that the heating during the second false twisting operation should be less than that during the first false twisting operation, and preferably this should be obtained by heating the yarn to a lower temperature (as opposed to simply a shorter time).

Preferably for both the first and second false twisting operations the yarn is run over the same heating means (to eliminate variations in temperature that may occur with separate or unconnected heating means) and preferably the heater is such that it has a temperature gradient in the direction of travel of the yarn over it so that the temperature of the heater at the point first contacted by the yarn is lower than the temperature at the point where the yarn leaves the heater.

An important feature of the heating arrangements mentioned above is that the yarn before its second passage over the heater leaves the heater at a position before that at which it left it during its first passage over the heater so that the point at which the yarn leaves the heater during its second passage is at a lower temperature than the point at which the yarn left the heater during its first passage over it. Also, the position at which the yarn leaves the heater during its second passage over it should be adjustable so that the desired characteristics in the finished yarn can readily be obtained, particularly when it is desired to take account of any variations in the yarn being processed. By using the common heater, once the position at which the yarn leaves the heater during its second passage over it has been correctly adjusted for a particular yarn, any variations in the heater temperature should affect both false twisting operations to approximately the same extent and so not have any noticeable effect on the final non-torque of the crimped yarn.

The heater preferably has one groove for each yarn path over it but a non-grooved heater can be used. It is highly desirable that the surface of the heater should be convex.

In one example where the machine is arranged to produce a substantially non-torque crimped false twisted yarn formed from 7 filament 20 denier nylon 66 the two stretches of the one yarn are pulled off their respective twisting heads of the group of three rollers at the same rate of about feet per minute and the twisting heads are rotated at about 200,000 revolutions per minute. The tensioning device through which the first stretch passes is adjusted to result in a tension of about 4 grams being exerted in the yarn. The twist imparted to the yarn on the entry side of the twisting heads is about turns per inch.

The length of the bowed faced heating member is about 24 inches and its temperature gradient is from C. at the end where the two stretches first contact with it to 225 C. at the other end. The adjustable yarn guide for the second stretch of the yarn is positioned so that the second yarn leaves the heated surface where its temperature is about 156 C.

It will be appreciated that various modifications may be made to various features of construction without departing from the scope of the invention, for example, two separate heaters may be provided and means may be associated with at least one of them whereby the length of contact of the yarn with it may be varied.

The magnetically restrained adjustable pulley may be replaced by a positively driven pulley the speed of which may be adjusted.

Each twisting head may either comprise the conventional arrangement in which the yarn is drawn up through a rotatable tubular element across which extends a cross bar or bail around which the yarn is wrapped and which tubular element is rotated by rollers grouped around it or each twisting head may comprise a group of rotatable wheels which engage the yarn directly at points around its circumference and spaced apart along its length.

I claim:

1. A method of crimping yarn comprising a first step of heating and then false twisting the yarn on the run in one direction; and a second step of heating the yarn to a lesser extent than in the first step and then false twisting the yarn on the run in the opposite direction to, and to an equal or greater degree than the false twisting in the first step; positively tensioning the yarn While it is being heated and false twisted on the run in said one direction by drawing the yarn under tension through the first step; and positively feeding the yarn through said second step.

2. A method as claimed in claim 1 in which the maximum temperature to which the yarn is subjected in the second step is less than in the first step.

3. A method as claimed in claim 1 in which the yarn is subjected to little or no tension during said second step.

4. A method as claimed in claim 1 in which the heating of the yarn in the second step is effected by the same heating means as used for the first step.

References Cited by the Examiner UNITED STATES PATENTS 3,041,813 7/1962 Enneking 57-157 X 3,041,814 7/1962 Held 57--15'7 X 3,071,838 1/196'3 Scragg 28-72 X 3,137,119 6/1964 Crouzet 57-34 X 3,165,881 1/1965 DeMoncuit et al. 57-34 3,270,492 9/ 1966 Fitton et al. 5734 FRANK I. COHEN, Primary Examiner.

MERVIN STEIN, D. E. WATKINS, Assistant Examiners. 

1. A METHOD OF CRIMPING YARN COMPRISING A FIRST STEP OF HEATING AND THEN FALSE TWISTING THE YARN ON THE RUN IN ONE DIRECTION; AND A SECOND STEP OF HEATING THE YARN TO A LESSER EXTENT THAN IN THE FIRST STEP AND THEN FALSE TWISTING THE YARN ON THE RUN IN THE OPPOSITE DIRECTION TO, AND TO AN EQUAL OR GREATER DEGREE THAN THE FALSE TWISTING IN THE FIRST STEP; POSITIVELY TENSIONING THE YARN WHILE IT IS BEING HEATED AND FALSE TWISTED ON THE RUN IN SAID ONE DIRECTION BY DRAWING THE YARN UNDER TENSION THROUGH THE FIRST STEP; AND POSITIVELY FEEDING THE YARN THROUGH SAID SECOND STEP. 